1. Field of the Disclosure
The disclosure generally relates to a method of collecting RDF data using Bluetooth™ signals that is suitable for implementation within a mobile device.
2. Related Technology
Radio direction finding (RDF) is a method of determining from received radio signals the direction in which the radio transmitter lies. A common method of performing RDF is to configure an array of antennas to receive the signals and determine the direction of the transmitter using the differences in phase and amplitude in the signals received at each antenna in the array. As input for the direction finding algorithms it is generally necessary to provide the relative phase and amplitude data for the received signal at each of the antennas within the array at a single given instant in time. This may be achieved by providing a separate receiver chain for each antenna so that the receivers can be sampled simultaneously (in parallel) or by switching between the individual antennas at a rate such that all the antennas can be sampled before the transmitted signal changes.
As mobile telephones, as well as other mobile devices, move towards becoming ubiquitous devices there is a desire to provide RDF capability within such mobile devices. It is already very common for such mobile devices to include a Bluetooth™ transceiver, which allows relatively short range (typically tens of meters) data communication to occur between Bluetooth™ enabled devices. There is therefore a desire to use Bluetooth™ transmissions in RDF within mobile devices. However, it is prohibitively expensive in terms of cost and physical space to provide a mobile device having a plurality of Bluetooth™ antennas each with their own receiver chain. Additionally, transmission rate for a Bluetooth™ signal is 1M symbols/s, with the symbols being transmitted using a frequency shift keying (FSK) scheme. It is not feasible To provide an array of antennas within a mobile device with the necessary switching speed to allow the antennas to be switched within a single symbol period.